Well I was cleaning the beast today and I keep hearing this humming noise, well I get inside the truck ( 05 Century)
and there is air coming out of the little vent right under the bottom bunk, so I lift the bunk and there is a long black box there and I guess there is a fan in there or something and its staying on and the truck is off, what is it and why is it staying on?

Is it a fuel fired bunk heater ? While they do blow very hot air when they are running maybe yours is malfunctioning and the fan is just sitting there running ? It is the only thing I can think of that would run with the key off. That's what it sounds like to me but if there was no hot air it isn't working right. Maybe the little fuel pump is shot or I believe there is some sort of ignition deal that wears out. 8) 8)

You no what you are right, I think I went looking again and on the control panel by the bunk there is a dial that says Wabash ( I think) and I guess my kids turned it on and it was blowing but it wasnt blowing hot air.

nevermind seems like it's bunk heater...probably says..."WABASTO"

Yeah sounds like maybe it's not working right. They are pretty awesome but what's not awesome is when it's like below 0 degrees out and in the middle of the night after the fuel is cooled down from the truck running all day the fuel starts to gel up in that little tiny fuel line feeding the heater and I wake up about 3 in the morning to the inside of my truck about 10 degrees and the "heater" is just sitting there blowing cold air around. It's not very fun getting out of bed to start the truck when that happens. I tried anti gel and all that but it still does it. It only did it about 5 or 6 times last year though 8) 8)

Ya Big Jeep you are right and TK that sucks I guess I'll keep the truck running in the winter.

I'd consider fixing it and maybe only idle if it's 10 degrees or colder, something like that might work. Mine worked great the rest of the time. Just when it was way cold out is when it would do that. They are quite a fuel saver. 8) 8)

If it is like my espar bunk heater I can just have the fan running to circulate the air. Are there any buttons besides the dial?

No the only thing there is the dial.